26 Conductivity of Aqueous Solutions. Port II. 



When the bomb is not in use, good water is left standing in the lower 

 part. The cover is inverted and the upper chamber similarly kept filled 

 with water. If for the next experiment a more dilute solution is to be 

 employed, the bomb must first be heated with good water to perhaps 218 

 for some little time. No amount of rinsing or soaking out at ordinary 

 temperatures will answer the purpose. There is on this account a great 

 saving of time effected by beginning with the most dilute solution to be 

 investigated, and afterwards measuring those more and more concentrated. 



Our measurements at 306 were carried out, for the most part, after 

 complete experiments up to 281 had been made, so that they usually con- 

 sisted merely of measurements at 26, 306, and again at 26. 



7. PROCEDURE FOR THE SPECIFIC-VOLUME MEASUREMENTS. 



To determine the specific volume of a solution at any temperature, such 

 an amount of solution is weighed into the bomb as will bring the liquid 

 level up onto the auxiliary electrode at that temperature. This amount was 

 determined by successive heatings with increasing volumes of solution. 

 A pipette of the form represented by fig. 8 was made for each 

 of the temperatures 218, 281, and 306. The stem is gradu- 

 ated between a and b, and the capacity up to these points is 

 roughly determined by weighing. The volume of the pipette 

 is made such that for water or dilute solutions it will deliver 

 the right amount into the bomb when filled up to the point b. 

 For more concentrated solutions the expansion is less, so that 

 more of the solution must be used. The graduations on the 

 pipette serve only as an indication of how much solution to take. 

 The exact amount used is obtained by weighing the pipette filled 

 and then again after discharging. During the weighing the tip 

 is covered with a small test tube c, which is held on by the 

 rubber band d. 



The bomb is first dried out by rinsing- it with alcohol and 



C" ft 



ether. The residue left by these solvents upon evaporation is 

 sufficient to affect the conductivity of the diluter solutions employed, so 

 that no attempt was made to determine the conductivity of such solutions 

 at the same time as their specific volume. The solution is boiled to expel 

 the air. This increases the concentration slightly ; but this is of no conse- 

 quence if, as was usually the case, the experiment was made solely to deter- 

 mine the specific volume. If it was also to serve for conductivity measure- 

 ments, the solution was boiled gently in a tall platinum vessel which was 

 weighed with its contents before and after boiling. This gave the loss of 

 solvent during the operation. Knowing this and the amount of solution 



